Picture
This color picture is made from images taken by the Galileo spacecraft about 14 minutes before its closest approach to Ida at a range of about 10,500 kilometers (6,500 miles). The color is enhanced in the sense that the camera is sensitive to near-infrared wavelengths of light beyond human vision; a natural color picture of this asteroid would appear mostly gray. There are brighter areas, appearing bluish in the picture, around craters on the upper left end of Ida, around the small bright crater near the center of the asteroid and near the upper right-hand edge (the limb). This suggests a difference in the abundance of or composition of iron-bearing minerals in these areas. Ida's moon also has a different color in the violet than any area on this side of Ida. (Courtesy NASA/JPL) This view of the asteroid 243 Ida was acquired by the Galileo spacecraft at ranges of 3,057 to 3,821 kilometers (1,900 to 2,375 miles) on August 28, 1993, about 3.5 minutes before the spacecraft made its close approach to the asteroid. This view shows numerous craters, including many degraded craters larger than any seen on Gaspra. The south pole is believed to be in the dark side near the middle of the asteroid. (Courtesy NASA/JPL) This image is the first full picture showing both asteroid 243 Ida and its moon Dactyl transmitted to Earth from NASA's Galileo spacecraft. Ida is the large object to the left and Dactyl is the small object to the right. This portrait was taken about 14 minutes before Galileo's closest approach to the asteroid, from a range of 10,870 kilometers (6,755 miles). Although Dactyl appears to be next to Ida, it is actually slightly in the foreground, closer to the spacecraft than Ida and is about 100 kilometers (60 miles) away from the center of Ida. (Courtesy NASA/JPL) This image shows three different stereo image pairs of Ida. They were acquired by the Galileo spacecraft during its approach to Ida. The top image pair is the lowest resolution and the bottom image the highest. The stereo, three-dimensional view can be seen by looking at the left image with the left eye and the right image with the right eye. Print a small version of the image on a page, hold the page close to your face, relax your eyes as if you were looking in the distance, and slowly move the page away from your eyes. The image pairs will merge together to become one image. It may take some practice to see the images in stereo. (Copyright © 1997 by Calvin J. Hamilton) This image is the most detailed picture of Dactyl taken by the Galileo spacecraft's camera. The camera fortuitously captured the previously unknown moon at a range of about 3,900 kilometers (2,400 miles), just over 4 minutes before the spacecraft's closest approach to Ida. More than a dozen craters larger than 80 meters (250 feet) in diameter are clearly evident, indicating that Dactyl has suffered numerous collisions from smaller solar system debris during its history. The larger crater on the terminator is about 300 meters (1,000 feet) across. At the time this picture was taken, Ida was about 90 kilometers (56 miles) away from the moon, outside this frame to the left and slightly below center. (Courtesy NASA/JPL) This is a topographic map of Ida. It is based upon the shape model of Peter Thomas and his colleagues. It was adapted by Phil Stooke and unlike other small body models, it is quite certain. (Courtesy A. Tayfun Oner) This composite image shows the asteroid 243 Ida as seen from the Galileo spacecraft during its approach on August 28, 1993. The six views were shuttered through the camera's green filter and show Ida's rotation over a period of about 3 hours 18 minutes. The asteroid makes a complete rotation every 4 hours 38 minutes; therefore, this set of images spans about 3/4 of Ida's rotation period and shows most of Ida's surface. By combining the information in these views with that from the highest resolution images returned from the spacecraft in September 1993, the size and shape of this irregular body can now be determined accurately The asteroid appears to be about 58 kilometers (36 miles) long and about 23 kilometers wide, with a very irregular shape and volume of some 16,000 cubic kilometers. The images are arranged in chronological order from a time 3 hours 51 minutes before closest approach (upper left), through upper right, middle left, middle right lower left and lower right (33 minutes before closest approach). The six images show Ida at the same scale throughout. Ida's rotation axis is roughly vertical in these images, and the rotation causes the right-hand end of Ida to move toward the viewer as time progresses. The first image was taken from a range of about 171,000 km (106,000 miles) and provides an image resolution of about 1,700 meters per pixel (the highest resolution achieved for Ida is about 25 meters per pixel). The second, taken 70 minutes later, is from 119,000 kilometers, followed by 102,000 kilometers, 85,000 kilometers, 50,000 kilometers, and 25,000 kilometers. The features on Ida are less sharp in the earlier views because of the greater distances. Prominent in the middle three views is a deep depression across the short axis of the Asteroid. This feature tends to support the idea that Ida may have originally been formed from two or more separate large objects that collided softly and stuck together. Also visible in the lower left view is an apparent linear albedo or reflectance boundary. Color images yet to be returned from the Galileo spacecraft may help resolve the question of whether or not the two ends of Ida are made of different materials. The Galileo imaging system captured this picture of the limb of the asteroid 243 Ida about 46 seconds after its closest approach on August 28, 1993, from a range of only 2480 kilometers. It is the highest-resolution image of an asteroid's surface ever captured and shows detail at a scale of about 25 meters per pixel. This image is one frame of a mosaic of 15 frames shuttered near Galileo's closest approach to Ida. Since the exact location of Ida in space was not well known prior to the Galileo flyby, this mosaic was estimated to have only about a 50 percent chance of capturing Ida. Fortunately, this single frame did successfully image a part of the sunlit side of Ida. The area seen in this frame shows some of the same territory seen in a slightly lower resolution full disk mosaic of Ida returned from the spacecraft in September 1993 but from a different perspective. Prominent in this view is a 2kilometer- deep 'valley' seen in profile on the limb. This limb profile and the stereoscopic effect between this image and the full disk mosaic will permit detailed refinement of Ida's shape in this region. This high-resolution view shows many small craters and some grooves on the surface of Ida, which gives clues to understanding the history of this heavily impacted object. The Galileo project, whose primary mission is the exploration of the Jupiter system in 1995-97, is managed for NASA's Office of Space Science by the Jet Propulsion Laboratory. Within seconds of its closest approach to the asteroid 243 Ida on August 28, 1993, the Galileo spacecraft's Solid State Imaging camera caught this glimpse of Ida's previously unknown moon orbiting the asteroid. One frame of a 15-image set designed to capture a view of Ida at the highest possible resolution landed by chance with its edge right on the little moon. The range from the spacecraft was about 2,400 kilometers (1,500 miles), and each picture element spans about 24 meters (80 feet) on the surface of the moon. Only a small sliver of the sunlit crescent is visible at the edge of the frame (which was shifted inward toward the center in this representation). Ida itself is outside this frame to the left and slightly below center, roughly 90 kilometers (56 miles) away. The dark side of this moon is illuminated by light reflected from the sunlit side of Ida, in the same way, that Earthshine brightens the dark part of Earth's Moon when it shows only a thin sunlit crescent, near 'New Moon'. The smoothly curving shape of the dark edge of Ida's moon can be seen on the left. The moon's observed dark side was just barely detectable by Galileo's camera; computer enhancement has made it easier to see in this picture. The visibility of the moon's dark limb has provided valuable information on the size and shape of the tiny moon, which measures about 1.2 x 1.4 x1.6 kilometers (0.75 x 0.87 x 1 mile). The little moon's relatively smooth egg shape contrasts markedly with the highly irregular shape of its parent, the asteroid Ida. This image was relayed to Earth from the Galileo spacecraft on June 8, 1994. The Galileo project, whose primary mission is the exploration of the Jupiter system in 1995-97, is managed for NASA's Office of Space Science by the Jet Propulsion Laboratory. This image is a closeup of the newly discovered moon of the asteroid Ida, provisionally designated '1993 (243) 1.' This is a magnified, processed version of the single view of the natural satellite transmitted so far by the Galileo spacecraft to Earth. Only 1.5 kilometers (1 mile) across in this view, the overall shape, size, rotation and orbital motion of the natural satellite are still unknown. The sun's illumination is coming from the upper right. The black 'gouge' in the body's shape toward the lower left is probably more apparent than real and is mostly a part of the shadowed night side of the little moon. A rugged landscape, including one or two craters, appears to be present, although the smallest features that can be detected in this picture are about 1/7th the diameter of the natural satellite. This picture was taken by Galileo during its flyby of Ida on August 28, 1993. Later in the spring of 1994, scientists hope to receive other views of Ida's moon which are currently stored on Galileo's onboard tape recorder; one of those images is expected to be at least three times sharper than this one. The Jet Propulsion Laboratory manages the Galileo Project for NASA's Office of Space Science. Pages: Home A Bit About Ida How Ida Got It's Name Discovery of Ida Formation Surface Escape Velocity Dactyl the Moon Picture